1. Field of the Invention
This system pertains to optical systems for projecting a beam of infrared or ultraviolet radiation, such as that emitted by a laser, for the purpose of guiding a beam-riding missile. In particular, the system of this invention pertains to means for automatically correcting the boresight error between the visual sightline through the optical system and the apparent center of the beam of radiation projected by the optical system, where the boresight error may vary with time.
2. Description of the Prior Art
A number of systems in the prior art provide for the correction of the boresight error between a visual line of sight and an infrared or visual beam of light where the error does not vary with time. These prior art systems generally are not automatic and are not continuous in their operation. As a consequence, they are of little or no use in correcting boresight errors that fluctuate as a function of time. For instance, if a "zoom" lens is included as part of the optical projection system so that the projected beam of radiation can be narrowed as the guided missile travels further from the projector, the operation of the "zoom" lens will introduce time varying boresight errors. Mechanical deformations and thermal stress also may cause fluctuating boresight errors.
A system for offsetting the apparent center of a projected beam of radiation for the purpose of compensating a missile guidance system for the effects of target motion is described by Miller Jr. et al. U.S. Pat. No. 3,807,658. The invention described in the present application utilizes the method described by Miller or any of the various other means available for offsetting the apparent center of the projected beam of light, in combination with a means for detecting boresight errors to automatical and continuously correct the boresight errors that are either fixed or fluctuate with time.